This invention generally relates to high frequency electrodeless lamps and, more particularly, to such lamps which are specially designed to have a relatively constant predetermined operating frequency with a minimum of output harmonics of the operating frequency.
High frequency electrodeless (HFE) lamps have received considerable attention in recent years as a possible replacement for the standard household incandescent lamps which convert electricity into light in a relatively inefficient manner. Fluorescent lamps are efficient converters of electricity into light, but their cumbersome size and their need for ballasting has limited their application in the household. HFE lamps, in contrast to the standard fluorescent lamps, can be fabricated in a relatively compact size.
U.S. Pat. No. 4,017,764, date Apr. 12, 1977 to Anderson, discloses an HFE lamp of the fluorescent type wherein a ferrite core is entirely contained within a phosphor-coated envelope. At column 5, lines 38-43 thereof, it is suggested to admix with powdered ferrite a polyimide resin to lower the permeability of the core.
U.S. Pat. No. 4,010,400, dated Mar. 1, 1977 to Hollister, discloses an HFE lamp which utilizes a ferrite core as a part of a tuned circuit output for a radio frequency energizing source.
U.S. Pat. No. 4,005,330 dated Jan. 25, 1977 to Glascock et al. discloses an HFE lamp wherein a closed magnetic core is positioned exteriorly of the environment of the envelope, but in energy transferring relationship with respect to the environment within the envelope.
U.S. Pat. No. 3,987,335, dated Oct. 19, 1976 to Anderson, discloses an HFE lamp of the fluorescent type wherein a ferrite core is only partially contained within the phosphor coated envelope.
U.S. Pat. No. 3,908,264, date Sep. 30, 1975 to Frieberg et al., discloses a high permeability core which constitutes a part of a tuned circuit wherein the resonant frequency of the circuit is calibrated by removing a portion of the core.
U.S. Pat. No. 3,150,340, dated Sep. 22, 1964 to Kalbfell, discloses a toroidal core for a high Q coil which includes an air gap in order to obtain a high value of Q for the coil.
An early design of electrodeless discharge lamp wherein the discharge is maintained by the fields established by a magnetic coil is disclosed in U.S. Pat. No. 1,813,580, dated Jul. 7, 1931 to Morrison.